MCF-7 cells of human breast cancer origin responded to estradiol (E) treatment with increased levels progesterone receptor (PgR) showing that which have undergone malignant changes can continue synthesize a specific protein under hormone control. These results were obtained by studying the effects addition and withdrawal E on PgR synthesis correlating this estrogen (ER) binding translocation nuclear processing reactions restoration unoccupied ER. In treated 1-5 days (.001-100 nM) basal...

The interactions of phytoestrogens with estrogen receptors were studied in the human breast cancer cell line, MCF-7. compounds tested coumestrol, genistein, and formononetin mycotoxins, zearalenone its reduced derivative, zearalenol. All but compete for binding [3H]- estradiol to unfilled cytoplasmic receptor or nuclear sites. Relative affinities are zearalenol HMP (high melting point isomer) > LMP (low = coumestrol> genistein formononetin. Dissociation constants estimated from competition...

The PR-A and PR-B isoforms of progesterone receptors (PR) have different physiological functions, their ratio varies widely in breast cancers. To determine whether the two PR regulate genes, we used human cancer cell lines engineered to express one or other isoform. Cells were treated with triplicate, time-separated experiments, allowing statistical analyses microarray gene expression data. Of 94 progesterone-regulated 65 are uniquely regulated by PR-B, 4 PR-A, only 25 both. Almost half...

Steroid receptor antagonists, such as the antiestrogen tamoxifen or antiprogestin RU486, can have inappropriate agonist-like effects in tissues and tumors. To explain this paradox we postulated that coactivators are inadvertently brought to promoters of DNA-bound, antagonist-occupied receptors. The human (h) progesterone (PR) hinge-hormone binding domain (H-HBD) was used bait a two-hybrid screen HeLa cDNA library, which yeast cells were treated with RU486. We isolated characterized two...

Ligand-dependent down-regulation that leads to rapid and extensive loss of protein is characteristic several nuclear steroid receptors, including human progesterone receptors (PRs). In breast cancer cells, >95% PRs are degraded 6 h after the start progestin treatment. The mechanism for unknown. We examined role PR phosphorylation by mitogen-activated kinases (MAPKs) in this process. Lactacystin calpain inhibitor I, specific inhibitors 26S proteasome, blocked progestin-induced...

Estrogen antagonists are widely used in the treatment of breast cancer, and studies their mechanism action may provide clues to an understanding tumor growth regulation mechanisms normal estrogen action. We have human cancer cells long term culture as vitro model study roles estradiol antiestrogens, tamoxifen nafoxidine, on cell progesterone receptor (PgR) induction. Tamoxifen is found dual dose-dependent estrogenic/antiestrogenic properties. With 1 micrometer tamoxifen, PgR induction...

This study attempted to show directly how antiestrogens (tamoxifen and nafoxidine) affect the estrogen receptor (ER) in MCF-7 human breast cancer cells. The mechanisms of action through unfilled ERs both cytoplasm (Rc) nuclei (Rn) this cell line were contrasted with effects estradiol (E) on binding nuclear processing reactions progesterone (PgR) synthesis. Within 5 minutes E bound Rc translocated it nucleus; also Rn directly. Beginning 30 after continuing for 3-5 hours a progressive...

Progesterone has biphasic effects on proliferation of breast cancer cells; it stimulates growth in the first cell cycle, then arrests cells at G1/S second cycle accompanied by up-regulation cyclin-dependent kinase inhibitor, p21. We now show that progesterone regulates transcription p21 promoter an unusual mechanism. This lacks a canonical response element. Instead, receptors (PRs) interact with through factor Sp1 third and fourth six binding sites located downstream nucleotide 154. Mutation...

When antagonist-occupied steroid receptors have agonist-like effects, the clinical consequences are grave. We present evidence that human progesterone B-receptors (hPRB) when occupied by antagonists, inappropriately activate transcription an unusual mechanism does not require canonical response element (PRE). In HeLa cells cotransfected with a PRE-tk-chloramphenicol acetyltransferase reporter and hPRB expression vector, strong is seen only activated agonist R5020, but also in presence of...

Human progesterone target tissues contain two receptors: B-receptors (hPRB), which are 933 amino acids in length, and A-receptors (hPRA), lack the N-terminal 164 acids. The isoforms differ functionally when they occupied by agonists or antagonists. We postulated that unique 164-amino acid, B-upstream segment (BUS) is part responsible for functional differences between have constructed a series of hPR expression vectors encoding BUS fused to isolated down-stream domains receptors. These...

Depending on the tissue, progesterone is classified as a proliferative or differentiative hormone. To explain this paradox, and to simplify analysis of its effects, we used breast cancer cell line (T47D-YB) that constitutively expresses B isoform receptors. These cells are resistant effects epidermal growth factor (EGF). Progesterone treatment accelerates T47D-YB through first mitotic cycle, but arrests them in late G1 second cycle. This arrest accompanied by decreased levels cyclins D1, D3,...

The subunit structure of mammalian cytoplasmic progesterone receptors (PR) has been difficult to study because these proteins are subject in vitro proteolysis; the nuclear PR is unknown. We have now developed an situ photoaffinity labeling method for that permits their subunits with minimal incubations. strategy use [3H]R5020, a synthetic photoactive progestin, and suitable incubation temperatures place into precise intracellular sites intact cells. cells, still intact, then irradiated UV at...

Sex differences and steroid hormones are known to influence the vascular system as shown by different incidence of atherosclerosis in men premenopausal women, or increased risk cardiovascular diseases women taking birth control pills estrogens. However, mechanisms for these effects tissues not known. Since actions target mediated receptors, we have looked cytoplasmic receptor proteins dogs. We find specific saturable sedimenting at 8S on sucrose density gradients estrogens (measured with...

Inappropriate activation of developmental pathways is a well-recognized tumor-promoting mechanism. Here we show that overexpression the homeoprotein Six1, normally developmentally restricted transcriptional regulator, increases TGF-β signaling in human breast cancer cells and induces an epithelial-mesenchymal transition (EMT) part dependent on its ability to increase signaling. EMT have been implicated metastatic dissemination carcinoma. Accordingly, used spontaneous experimental metastasis...

The synthetic radiolabeled androgen methyltrienolone-17βhiydroxy-17α-methyl-estra-4,9,ll-trien-3-one (R1881) is superior to the native ligand 5α-dihydrotestosterone (DHT) in measurement of receptor (AR), especially tissues where DHT binds with high affinity plasma proteins addition or rapidly metabolized inactive derivatives. However, R1881 also progesterone (PgR), as shown by its ability complete for [3]-promestone-17α,21-dimethyl-19-nor-pregna-4,9-diene-3,20-dione (R5020) binding 8S PgR on...

Abstract Purpose: No study has yet analyzed whether changes in relative expression levels of progesterone receptor (PR) isoforms A and B human breast tumors have significance predicting clinical outcome. Human PRs are ligand-activated nuclear transcription factors that mediate action. Their presence is used to predict functional estrogen receptors (ERs) and, therefore, also the likelihood response endocrine therapies disease prognosis. The two PR isoforms, PR-A PR-B, possess different vitro...

Background —Estrogens have vascular effects through the activation of estrogen receptors (ERs). In addition to ERα, first ER be cloned, a second subtype called ERβ has recently been discovered. Methods and Results —Using reverse-transcriptase polymerase chain reaction assay that employs same primer pair simultaneously amplify ERα transcripts, we found is form predominantly expressed in human smooth muscle, particularly women. The transcriptional 2 ERs transfected HeLa cells differed....